JP2722063B2 - Motorcycle cantilever swing arm - Google Patents

Description

The present invention relates to a cantilever type swing arm of a motorcycle,
The present invention relates to a device having improved rigidity. [Background Art] A motorcycle in which a rear wheel is supported by a cantilever swing arm is known, and an example thereof is described in Japanese Patent Application Laid-Open No. 61-129386. In this rear wheel support device, the rear end side of the swing arm is a single member that does not branch into a forked shape, the rear wheel is arranged on one side, and a chain driven sprocket is arranged on the other side, Both are connected by a drive shaft. [Problems to be Solved by the Invention] By the way, since the motorcycle is grounded only by the front and rear wheels, it is necessary to reduce the deflection of the vehicle body during a disturbance with the road surface. The amount of displacement of each contact point during a disturbance must be reduced. In order to reduce the displacement of the ground contact point, it is necessary to increase the torsional rigidity and the lateral rigidity of the rear swing arm on the rear wheel side, which is the driving wheel. In order to provide such rigidity sufficiently, it is sufficient to increase the cross-sectional shape of the swing arm. However, simply increasing the size of the swing arm increases the size and weight of the entire swing arm. Besides, not only considering the rigidity of the swing arm itself, but also considering the overall suspension including the actual behavior of the rear wheel when the rear wheel is suspended, the ultimate balance of weight reduction and compactness etc. Rigidity cannot be increased. The present invention has been devised in view of the above circumstances, and an object of the present invention is to increase the rigidity of the swing arm without changing the external dimensions of the swing arm, and at the same time achieve weight reduction, and An object of the present invention is to provide a swing arm capable of correcting a torsion center downward. [Means for Solving the Problems] The cantilever swing arm of the motorcycle according to the present invention includes:
The vehicle body frame has a single swinging portion that pivotally supports the front end vertically and extends rearward.The axle is traversed to the rear free end side of the swinging portion. In a hollow motorcycle swing arm that cantileverly supports the rear wheel adjacent to the side of the swinging portion by attaching the wheel, the center of torsion in the cross section of the swinging portion is larger than that in the approximate center of the cross section. The lower wall surface is made thicker than the upper wall surface so as to be located below. [Operation of the Invention] Since the lower wall surface of the hollow swing arm is made thicker than the upper wall, rigidity, particularly lateral rigidity, is increased without making the entire wall thick. Also, as a result, the position of the torsion center is corrected downward as compared with the case where the overall thickness is made uniform, so even if the swing arm is twisted by the same angle, it is supported adjacent to this side. The amount of displacement of the ground contact point of the rear wheel is smaller than when the position of the torsion center is the center. That is, since the amount of displacement of the rear wheel at the ground contact point is reduced by correcting the position of the torsion center downward, it is possible to reduce the vibration of the motorcycle body during a disturbance,
The same effect can be obtained as when the torsional rigidity of the swing arm itself is increased. Therefore, the rigidity required as a suspension device is increased without increasing the external dimensions, and the entire swing arm is reduced in weight. FIG. 1 to FIG. 4 show an embodiment of the present invention. 1 is a rear view of a motorcycle to which the present invention is applied, FIG. 2 is a plan view showing a partially cutaway cantilever type swing arm according to the present embodiment, and FIG. 3 is a cantilever type swing arm. FIG. 4 is a perspective view of the swing arm, and FIG. 4 is a view schematically showing a cross section of the cantilever swing arm. FIG. 1 is a right side view of a rear wheel suspension unit of a motorcycle. That is, a power unit including the V-type engine E and the transmission chamber M is supported by the body frame F. A cantilevered swing arm 1 having one end pivotally mounted on a pivot P is provided at a rear portion of the body frame F. A curved space, which will be described later, is formed on the front side of the swing arm 1, and the cushion unit 2 is vertically disposed in this space in the vertical direction. The upper end of the cushion unit 2 is pivotally attached to a cushion bracket B integrally formed from the vehicle body frame F, and the lower end is pivotally attached to the bottom of the swing arm 1 via a link rod 3. On one side of the other end of the swing arm 1, a rear wheel 4 is cantilevered via an axle 5. On the other side of the swing arm 1, a sprocket 6 is attached to an end of the axle 5 via a known damper unit 7. The sprocket 6 reduces the driving force transmitted by the chain 8 and transmits it to the rear wheel 4. In addition, a plurality of exhaust pipes 9 are provided through an exhaust port of the engine E.
And these are collected in a collecting portion 9a disposed below the mission chamber M. Further, from the collecting portion 9a, a collecting exhaust pipe 9b extends obliquely to the swing arm 1, and a muffler 9c is provided at a rear end thereof. Although not shown, the muffler 9c is supported on the vehicle body frame F via a bracket. 2 and 3 show the swing arm 1 of the present embodiment in detail. The swing arm 1 is a cast product made of a light alloy such as aluminum having a substantially Y shape in a top view, and is provided with arms 10a and 10b which are bifurcated on the front left and right. The arms 10a and 10b are connected by a curved horizontal portion 11, and brackets 12a and 12b for attaching the link rod 3 to the shaft are provided on the bottom side of the horizontal portion 11. Arms 10a, 10b
The pivot mounting portions 13a and 13b are provided at each of the ends. Further, a curved space 14 is formed by being surrounded by the horizontal portion 11 and the arm portions 10a and 10b, where the cushion unit 2 is formed.
Is arranged. In this figure, the cushion unit 2 is indicated by a virtual line. The left pivot mounting portion 13a is located on the line L of the chain 8 (see FIG. 1), and the needle bearing 15 is fitted inside thereof. On the other hand, a ball bearing 16 is fitted in the pivot mounting portion 13b. The bearings are changed in this way because the swing arm 1 is of a cantilever type, so that the driving force applied to the sprocket 6 increases the shared load on the pivot mounting portion 13a and receives a thrust load. . A collecting portion 9a of the exhaust pipe 9 is provided below the pivot mounting portions 13a and 13b, and a large-diameter collecting pipe 9b corresponding to a large displacement is formed from the arm portion.
It is arranged to overlap under 10b. However, since the distance between the two is large in the vertical direction, they do not buffer each other. Further, a center portion of the swing arm 1 in which the arm portion 10b is integrated with the arm portion 10a is formed as a curved portion 17 which is curved outward so as to avoid the center line O of the vehicle body, thereby providing a space on the vehicle body center side.
18 are formed. Swing arm 1 in this space 18
Of the rear wheel 4 which is pivotally supported by the rear end portion. As shown in FIG. 2, a holder 19 is provided at one end of the swing arm 1, and a shock absorber 7 integrally with the sprocket 6 is mounted on the left side surface thereof. The shock absorber 7 is for damping the transmission shock of the driving force. A well-known eccentric unit 20 for adjusting the position of the axle 5 in the front-rear direction is provided in the holder 19. In this eccentric unit 20,
The axle 5 is eccentrically supported. The axle 5 is a hollow member formed with a step so that the tip 5a is tapered. If the tip 5a side of the axle 5 is made thinner as described above, when the tip 5a is inserted into a bearing holder provided on the inner surface side to mount the axle 5 to the eccentric unit 20, the inner peripheral surface of the bearing holder And the large diameter portion of the axle 5, the tip 5a is always on the center line of the bearing holder and is guided so as not to touch the inner peripheral surface of the bearing holder. Therefore, the mounting work of the axle 5 becomes smooth. As shown in FIG. 2, a male screw portion is formed at the tip 5a, and this portion projects downward from the shock absorber 7 and is fastened by an axle nut 5b. As a result, the axle 5 is fixedly mounted in the axial direction. A flange 21 is formed integrally with the other end of the axle 5. A hub 22 of the rear wheel 4 is in contact with a side surface of the flange 21 and is attached by a bolt 23 and a nut 24 at equal intervals on a concentric circle. This allows the rear wheel 4 to be attached and detached only on one side (upper side in the figure) of the swing arm 1 on the flange 21 side. Reference numeral 25 in the drawing is a spoke. A brake disk 26 of a disk brake device is also attached to the flange 21 by bolts 27 and nuts 28. Further, a caliber 29 is provided at the rear of the axle 5 with the brake disk 26 interposed therebetween. The caliper 29 is formed at one end of a torque rod 29a (see FIG. 1), and the other end of the torque rod 29a is connected to the swing arm 1
It is attached to the boss 1a integrally formed thereon. As shown in FIG. 2, the operating center Ca of the axle 5 is set at a position where the swing of the swing arm 1 is minimized. That is, the driving forces applied to the sprocket 6 and the rear wheel 4 are T1 and T2 (T1> T2), respectively, and the distance from the operating center Ca to the sprocket 6 and the rear wheel 4 are S1 and S2, respectively. Assuming that the radii of 4 are r and R, respectively, and the moments given from the rear wheel 4 and the sprocket 6 to the working center Ca are balanced, r · T1 = R · T2 and S1 · T1 = S2 · T2. . Therefore, S1 / S2 = T2 / T1 = r / R.
If Ca is set, the swing of the swing arm 1 can be minimized. FIG. 4 schematically shows a cross-sectional structure of the swing arm 1. As shown in this figure, the swing arm 1 is hollow, but the wall thickness thereof is not uniform, and the upper surface 30 and the left and right sides 31, 32 have a thickness t1, whereas only the lower surface 33 has Is the thickness t2 (t1 <t2), which is a thick portion. For this reason, the torsion center of the swing arm 1 is corrected downward and shifted to the thicker side as compared with the case where the thickness is uniform throughout. That is, assuming that the actual torsion center is C and the assumed torsion center in the case where the entire thickness is uniform is C0, the torsion center C is shifted toward the lower surface 33 by l1 with respect to the assumed torsion center C0. Become. Moreover, the lateral rigidity is increased by the thick structure of the lower surface 33. FIG. 7 is a view showing a state in which the swing arm 1 is twisted by the same angle about the torsion center C0 and C. FIG.
4b shows the state of the rear wheel when it is twisted clockwise by 20 ° about the torsion center C. As is apparent from this figure, when the torsion is applied to the swing arm 1 and the rear wheel 4 is twisted around the torsion center C, the torsion center C is lower than the same C0 by l1. Even with a twist angle, the displacement of the rear wheel 4a at the contact point of the rear wheel 4a is m2, whereas the displacement of the rear wheel 4b is m1 which is smaller than this, and the displacement of the contact point of the rear wheel 4 at the contact point is small. This is the same as increasing the torsional rigidity of the swing arm 1 itself. Various specific cross-sectional structures capable of realizing such correction of the torsion center are possible. For example, the one shown in FIG. 5 has a semi-cylindrical section. In this case, the top
Numeral 40 is a curved surface, and only the lower surface 41 is flat. Even in this case, the torsion center C is located closer to the lower surface 41 by l2. Also in this case, the thickness of the lower surface 41 is
By increasing the thickness, the lateral rigidity is increased. Further, in FIG. 6, the upper surface 50 and the outer surface 51 (on the opposite side of the axle) have a thickness t3, whereas the inner side surface 52 and the bottom surface 53 have a thickness t4 (t4> t3). Moreover, ribs 54 and 55 are formed by projecting both side end portions of the bottom surface 53 downward. Therefore, in this case, the torsional center C is remarkably shifted inward and downward by l3 and l4, and both effects of increasing the lateral rigidity and increasing the torsional rigidity are achieved. [Effect of the Invention] In the present invention, the lower wall surface of the hollow swing arm is made thicker than the upper wall. Therefore, without making the whole thick, rigid,
Particularly, the lateral rigidity can be improved. Also, as a result, the position of the torsion center is corrected downward as compared with the case where the overall thickness is made uniform, so even if the swing arm is twisted by the same angle, it is supported adjacent to this side. The amount of displacement of the ground contact point of the rear wheel is smaller than when the position of the torsion center is the center. That is, since the amount of displacement of the rear wheel at the ground contact point is reduced by correcting the position of the torsion center downward, the torsion of the motorcycle body during a disturbance can be reduced.
The same effect as when the torsional rigidity of the swing arm itself is increased can be obtained. Therefore, the rigidity required as a suspension can be increased without increasing the external dimensions, and the entire swing arm can be reduced in weight as much as possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 show an embodiment of the present invention. FIG. 1 is a side view of a rear wheel suspension device of a motorcycle on the left side in the traveling direction, and FIG. Is a partially cutaway plan view, FIG. 3 is a perspective view of a main part, and FIG. 4 is a schematic view corresponding to a cross section taken along line IV-IV of FIG. FIGS. 5 and 6 show a fourth embodiment of the present invention.
It is a schematic diagram of the part equivalent to a figure. FIG. 7 is a view showing a state where the swing arm in FIG. 4 is twisted. (Description of Signs) 1 ... Swing arm, 4 ... Rear wheel, 5 ... Axle, 8 ... Chain, 9 ... Muffler, 10a, 10b ... Arm, 13a, 13b ... Pivot mounting part, 30, 40, 50 ... Top surface, 33, 41, 53 ... lower surface (thick part), C0, C ... torsion center.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Keiichiro Takagi               1-4-1, Chuo, Wako-shi Book Co., Ltd.               Field Technology Research Institute (72) Inventor Yumi Sasaki               1-4-1, Chuo, Wako-shi Book Co., Ltd.               Field Technology Research Institute                (56) References JP-A-61-129386 (JP, A)                 58-163383 (JP, U)                 Shokai Sho 61-95688 (JP, U)

Claims (1)

(57) [Claims] The vehicle body frame has a single swinging part that pivotally supports the front end vertically and extends rearward, and crosses the axle to the rear free end side of the swinging part. In a hollow motorcycle swing arm that cantileverly supports the rear wheel adjacent to the side of the swinging portion by attaching the wheel, the torsion center in the cross section of the swinging portion is larger than the substantially central portion of the cross section. A cantilever type swing arm for a motorcycle, wherein a lower wall surface is thicker than an upper wall surface so as to be positioned below.